The invention relates to a cathode-ray tube having a glass envelope portion and a gettering device which comprises a getter holder in the form of an annular metal channel, which gettering device is urged against an internal wall portion of the glass envelope portion by means of a resilient metal strip connected to a component of the tube. The metal channel is connected via a metal connection strip to the resilient metal strip and is kept spaced from the wall portion by means of a metal support member.
The invention furthermore relates to a gettering device suitable for such a tube.
Such a cathode-ray tube is known from German Auslegeschrift No. 1950230, corresponding to British Pat. No. 1,274,289. In the tube the metal support member consists of a piece of wire, the two ends of which are bent at right angles and are curved convexly with respect to the tube wall. The spacing between the convexly curved end sections is approximately equal to the diameter of the annular getter holder. The convexly curved end sections determine the supporting points for the gettering device on the tube wall. Therefore, in this known construction the supporting points are directly below and at a very short distance from the annular getter holder.
In cathode-ray tubes it is usual to use gettering devices of the type which are inductively heated to cause the gettering metal to be evaporated. During the evaporation process the temperature of the getter holder and its filling may increase to approximately 1300.degree. C. The temperature of the support members may reach undesirably high values as a result of thermal radiation and thermal conductivity. This may result in glass damage at the area where the support member contacts the glass wall of the tube. Experiments have demonstrated that such glass damage does not occur when the temperature of the support member at the area where it contacts the glass wall does not exceed approximately 700.degree. C. It becomes more difficult to satisfy this requirement as the diameter of the annular holder of the gettering devices become smaller.